Researchers at the University of Illinois have demonstrated a new, easy way to decontaminate 3M’s disposable N95 masks for reuse: Put the mask in an electric cooker. It can be a rice cooker or a pressure cooker. You can even use your oven.
The study comes after months of PPE shortages in the United States, leading scientists to search for methods of decontaminating N95 masks, among them: using a microwave to steam the masks, though that technique may require you to source a few extra supplies to do the job. The Instant Pot method works with things you already have.
So how exactly do you sterilize an N95 in an electric cooker? The researchers started with a $50 Farberware pressure cooker, one of many less expensive Instant Pot clones on the market. They lined the bottom with paper towels (they have demonstrated it with cloth towels too), to ensure that the masks did not touch the heating element at the bottom. Then they stacked several masks on top.
Once that was done, they sealed the lid and set a cooking cycle that would maintain 212°F for 50 minutes. On the Farberware, the setting reads “P03.” Researchers tell us that’s a setting for cooking rice, which makes sense. (Water boils at 212°F, so it’s the temperature at which you cook rice.) But they recommend you consult your manual to check the temperature of various settings to find one that will work for you. No water is poured into the pot at any time; the sterilization requires a completely dry cycle.
You can also use an oven if you don’t have a countertop cooker. The catch is that most ovens won’t let you target 212°F specifically, the way a cooker will. That means you may have to settle for 200° or 225°, but the researchers warn that if you go hotter than 212°F, you could hurt the mask. Go cooler, and it could take longer to sterilize.
The good news is that this process is repeatable. Researchers decontaminated masks 20 times, showing that SARS-CoV-2 and other coronaviruses were destroyed on all parts of the mask. Meanwhile, components such as the elastic headband stayed intact. After sterilization, researchers tested the filtration and found that it still filtered 95% of particles down to 0.3 microns—what makes the N95 such a powerful tool in the fight against COVID-19.
If you’d like to try the technique yourself, all you need is a cooker, a paper or cloth towel, and the right setting. Just remember that, unlike just about everything else you cook in an Instant Pot, you don’t add water.